N4ADE
Member
anyone know of any usb devices that are good for recording 5 or more scanners something that is cheep
around $100 or less preferably?
around $100 or less preferably?
usb audio in device
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OhioX
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OhioX
Member
I guess, you mean USB sound cards, right?
N4ADE
Member
something that just has audio in ports i dont need audio out i guess a pure recording device
Ground loop isolation
Has anyone been using these on a scanner? I bought the 3-pack off ebay. They work nicely when used as they're supposed to be (with a mic) attached. However, when I attach a scanner (headphone or speaker out) even with the volume down to nothing on the scanner, there is a bit of hum and the (AGC??) sound card is fighting me. Sounds to me like an impedance mismatch. Any cheap fixes for these cheap devices that anyone is using?
Thanks
Has anyone been using these on a scanner? I bought the 3-pack off ebay. They work nicely when used as they're supposed to be (with a mic) attached. However, when I attach a scanner (headphone or speaker out) even with the volume down to nothing on the scanner, there is a bit of hum and the (AGC??) sound card is fighting me. Sounds to me like an impedance mismatch. Any cheap fixes for these cheap devices that anyone is using?
Thanks
Are you asking if anyone is using these USB sound cards or if anyone is using ground loop isolators?
I guess that depends on what you call cheap. Since the sound cards only cost $1 each, that should leave a little in the budget for the rest of what is needed.
I have a surplus store near me and bought a couple dozen audio transformers. I wired them in a step-down configuration since I am using speaker out from the scanners and feeding that to mic in of the sound cards. I have the volume on the scanners set to about 10:30 and the input sliders on the computer set to about 50%. The exact setting depends on what/who you are receiving though.
I just wrote this in another thread, but what I found was causing the hum was a lack of ground from the scanner. It happens because the headphone jack is used instead of the EXT SP jack. Hand-held scanners usually don't have the EXT SP jack.
All the headphone jacks on scanners I have are wired so that the user can plug in a stereo or mono headphone and both sides will function. To do this the ground (sleeve) of the headphone jack is wired to ground through a resistor in the scanner. This causes a ground loop and can cause a hum or crosstalk. If all you have is a headphone jack, you may be able to eliminate the problem by using a ground from the external power supply (which is powering the scanner) or the antenna.
I have a surplus store near me and bought a couple dozen audio transformers. I wired them in a step-down configuration since I am using speaker out from the scanners and feeding that to mic in of the sound cards. I have the volume on the scanners set to about 10:30 and the input sliders on the computer set to about 50%. The exact setting depends on what/who you are receiving though.
I just wrote this in another thread, but what I found was causing the hum was a lack of ground from the scanner. It happens because the headphone jack is used instead of the EXT SP jack. Hand-held scanners usually don't have the EXT SP jack.
All the headphone jacks on scanners I have are wired so that the user can plug in a stereo or mono headphone and both sides will function. To do this the ground (sleeve) of the headphone jack is wired to ground through a resistor in the scanner. This causes a ground loop and can cause a hum or crosstalk. If all you have is a headphone jack, you may be able to eliminate the problem by using a ground from the external power supply (which is powering the scanner) or the antenna.
Can you tell us exactly what 'audio transformers' you bought and how you wired it all up? I know many people use the generic car stereo ground loop isolators, but in my feeds they don't always seem to work. Any help is appreciated!!!
What scanners do you have? I have tested your theory on my BCD996's and it doesnt seem to make a difference if I use the headphone jack or the speaker jack, I still get a bass hum when the feed is idle. The only difference is I have to set the levels lower if using the speaker jack over the headphone jack.
I have also noticed that using the REC out jack of the 996 is not much better since I am not using a typical LINE in on a normal sound card. I am using the MIC in on the $1 USB 3D Audio devices.
I know there are people out there using the $1 USB 3D Audio devices and have eliminated any background noise and have a crystal clear feed when no voice is present. I have tried all the suggestions in the Live Audio Wiki from RR. Any help from anyone is greatly appreciated?
Is it a ground?
I liked the idea of isolation transformers for the audio for a host of reasons. All scanners are being fed from the same antenna (well one or two are on a different antenna); all scanners are powered from wall warts; all scanners feeding USB cards.... And to get a low impedance between all these grounds can be tough. So I chose to isolate each scanner's audio as well.
Ground loop isolators will help you if you have a ground loop. But they are not magical and often there are still some other ground paths. Some people have had good luck with those $16 transformers from Radio Shack. I did not want to do that for as many scanners I am an using.
I made a point of saying I went to a surplus store because the transformer is not critical. You could use a 600:600 telephone line transformer and most would work fine. I found some transformers designed for audio with a 10:1 ratio. These would drop my signal by a factor of 10 to 1, which is what I wanted to do to get the signal closer to microphone level from speaker level.
The bulk of the scanners are PSR-400s but also have some BC780XLTs. If I connect to the headphone jack - hum, if I use EXT SP no hum. The headphone jack from a BC3000XLT worked fine, but all other scanners are base models.
I don't have one of those scanners presently, or a schematic for it. So I am uncertain about that model.
I am one of them. I do notice better quality sound from the PSR-400s; of my two feeds to RR one is from a PRO-433 and the other a BC780XLT.
I did not find that info useful. There are two ways I approached the problem, the first is to determine if the "ground" side of your audio output jack (whichever one you use) is in fact GROUND. Take an ohm meter and measure resistance to antenna ground, external power ground or a known device ground. If you get more than a few ohms (10 is way too much), connect the good ground to the ground of the audio feeding your computer.
I liked the idea of isolation transformers for the audio for a host of reasons. All scanners are being fed from the same antenna (well one or two are on a different antenna); all scanners are powered from wall warts; all scanners feeding USB cards.... And to get a low impedance between all these grounds can be tough. So I chose to isolate each scanner's audio as well.
Since I am using the USB sound cards and removing the plastic casing - can I solder a lead on the USB sound card PCB at teh mic jack gound terminal and run the lead to a screw on the back of the scanner - will that cure all?
My first thought - are you sure that screw on the back of the scanner is a scanner ground? What sometimes seems like should be ground may not be.
I don't want to get into the science of proper grounding for audio signals, especially microphone level signals. While a "secondary ground" might or might not reduce some hum, I don't want to go so far as to say it "will cure all".
The problem: there is no direct ground on the headphone jack on many scanners.
One solution: use audio from the headphone jack as the 'hot' signal; use a good ground as the ground side of the signal (from the antenna, external power connection, etc). Do this at the radio end so that the audio is somewhat shielded between the scanner and the sound card mic input.
I was generalizing, but you're right - I am not sure.
My solution for the REC out jacks was the audio transformer circuit inline (cutting a shielded audio patch cord in half and soldering in the transformer.) For the speaker and headphone jacks I am putting in a 40db attenuation circuit too.
Thanks for all the help!
I made my own cables, with a transformer, too. I used stereo plugs for each end but did not wire the ring (only tip and ground). The scanner is a mono signal anyway, and I am feeding them to a mic input (mono) on the computer side.
I used a transformer with about a 10:1 ratio and did not use resistors. I know it is not as much of a drop as you're trying to get, but I found I didn't really need it. You can adjust the scanner volume to about 10 or 11 o'clock and then set the input level on the computer for best modulation (about 50% of fullscale for me). If a signal from the scanner is too "loud", then you can set the volume there lower. If the input on the sound card is not ideal, you can adjust the fader accordingly.
What I did was go through each stage that the signal passes to resolve any issues with clarity. Connect a headphone directly to the scanner. Is that clean? Quite frankly I have a couple of scanners here that do not sound as good as the others. The feed cannot sound any better than that.
What I did next was to connect my headphones to the speaker out of the sound card which the scanner was connected. I am using separate USB sound cards, but each has a mic in and speaker out connection. I had to go into the Windows mixer so that the audio was routed to make this work, but it let me hear the signal after being digitized by the sound card.
On day 1 of setting all this up, long before I ever considered streaming to RR, this is the point where I could hear a horrible hum. I had to "jump through hoops" to clear up the sound from a hand-held scanner (except the BC-3000XLT), but it was clear from base models (PSR-400/etc) when I connected to the EXT SP jack.
I have also found that when the sound level is very low it can have some interesting artifacts. So I used a digital level meter to visually display the sound level from each input so I can set and maintain a good level.
Once all of the above was working, I set up ScannerCast to stream locally. Then I logged into it from another computer on my network and listened via WMP and WinAmp.
I used a transformer with about a 10:1 ratio and did not use resistors. I know it is not as much of a drop as you're trying to get, but I found I didn't really need it. You can adjust the scanner volume to about 10 or 11 o'clock and then set the input level on the computer for best modulation (about 50% of fullscale for me). If a signal from the scanner is too "loud", then you can set the volume there lower. If the input on the sound card is not ideal, you can adjust the fader accordingly.
What I did was go through each stage that the signal passes to resolve any issues with clarity. Connect a headphone directly to the scanner. Is that clean? Quite frankly I have a couple of scanners here that do not sound as good as the others. The feed cannot sound any better than that.
What I did next was to connect my headphones to the speaker out of the sound card which the scanner was connected. I am using separate USB sound cards, but each has a mic in and speaker out connection. I had to go into the Windows mixer so that the audio was routed to make this work, but it let me hear the signal after being digitized by the sound card.
On day 1 of setting all this up, long before I ever considered streaming to RR, this is the point where I could hear a horrible hum. I had to "jump through hoops" to clear up the sound from a hand-held scanner (except the BC-3000XLT), but it was clear from base models (PSR-400/etc) when I connected to the EXT SP jack.
I have also found that when the sound level is very low it can have some interesting artifacts. So I used a digital level meter to visually display the sound level from each input so I can set and maintain a good level.
Once all of the above was working, I set up ScannerCast to stream locally. Then I logged into it from another computer on my network and listened via WMP and WinAmp.
If you are using MIC input - you must build your own cable and not wire the ring - the MIC jack applies +5 bias ( +5V through a few kiloohm resistor) to the ring so it can power electret microphones. A small number of non-standard soundcards can have the bias voltage wired to the tip - be careful. A few cards have a jumper which enables or disables the power to the microphone jack. If the jumper is put on, the bias voltage is wired to the tip. Newer motherboards with stereo microphone support provide the bias voltage for both the tip and ring.
I still don't have my set up perfect, but its getting better with the correct shielded cable(s), attenuation, and isolation. Now, I seem to be having issues with Windows side of things... the MIC input controls don't appear to be making any difference, including when I turn the input completely down.
WA1ATA
Member
You could try to move the attenuation right to the jack. If you are picking up noise between the transformer and the card, putting the attenuator resistors right on the jack would reduce that noise.
It's by no means a sure bet, but it's simple to try.
Final configuration is the following...
Isolation: 1Kohm shunt to ground for noise isolation (photo 1)
Ring +5: remove center ring connection from jack to prevent voltage feed into audio path. (photo 2)
[Use Radio Shack Attenuating cable if level adjustment is necessary.]
This was the best I could do.
Isolation: 1Kohm shunt to ground for noise isolation (photo 1)
Ring +5: remove center ring connection from jack to prevent voltage feed into audio path. (photo 2)
[Use Radio Shack Attenuating cable if level adjustment is necessary.]
This was the best I could do.
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And today I tested an even better solution... true 'line-in' and excellent A/D converter ($11.00 each at Amazon.com)
Comes with headphones and two adapter cables that you dont need (but those alone are worth the price of the product.)
SoundTech Professional Audio Systems - Products > Home Recording > USB Audio Interface (STUSB10M)
Comes with headphones and two adapter cables that you dont need (but those alone are worth the price of the product.)
SoundTech Professional Audio Systems - Products > Home Recording > USB Audio Interface (STUSB10M)
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Just to be sure I'm understanding the process here....the 1K ohm resistor is between the tip and ground?
I'm working on a project, and want to incorporate this, but need to be sure first.
That is correct - see my diagram from the above post again if you want more details on the circuit. You can go anywhere between 10k and 1k (might be able to go as low as 750 ohm and still get your audio to pass through.)
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